Exploring the unexpected electrochemical dynamics of lithium vanadyl phosphate electrodes in zinc battery systems

Abstract

Zinc-ion batteries (ZIBs) have garnered substantial attention as a potential alternative to Li-ion batteries (LIBs) because of their low cost and high safety. However, commercialization challenges persist for ZIBs, which are primarily attributed to the absence of electrode materials with sufficient energy density. In this study, we initiate the exploration of β-LiVOPO₄ as a high-energy and high-power ZIB cathode due to its robust 3D structural framework and elevated operating potential. Specifically, we achieved a high working voltage of 1.61 V vs. Zn/Zn²⁺ for β-LiVOPO₄. The cathode delivered a discharge capacity of 114.1 mA h g⁻¹ at a current density of 100 mA g⁻¹ with considerable cyclability and rate performance. We explored the storage mechanism of the β-LiVOPO₄ cathode using various characterization techniques, including in situ synchrotron X-ray diffraction (XRD), ex situ X-ray absorption spectroscopy, ex situ XRD, and theoretical calculations. During cycling, a reversible and stable phase transition through capacitive-based surface reactions and repeated Li⁺/Zn²⁺ (de)insertion were maintained. This contributed to the high electrochemical performance of β-LiVOPO₄ when used as a ZIB cathode.